Vacuum Furnace Degassing
Vacuum furnace degassing removes dissolved gases from metals and filler metals by vacuum to avoid pores and voids in the weld.
Physical-Chemical Mechanism of Action
Vacuum degassing works by removing air from the furnace. This drastically lowers the gas pressure and allows dissolved gases in the metals to escape. The low pressure condition promotes diffusion of the gases to the surface of the material, where they can outgas.
Metallurgical Relevance & Risks in Welding
Without degassing, dissolved gases can remain in the weld seam and lead to pores and voids. These can impair the strength and mechanical properties of the seam, which can lead to cracking and failure in service. Careful degassing prevents these problems and improves the quality of the weld.
Workshop Practice & Instructions
Before the brazing process begins, the furnace is placed under vacuum. This is done by using a vacuum pump system that removes air from the furnace. The pressure condition should be below 10^-3 mbar to ensure effective degassing. The degassing time varies depending on the material and brazing process, but it is common to wait at least 30 minutes to ensure that the gases are released. After degassing, the furnace heating system is activated and the brazing material is prepared.